The Big O is a tV series anime that premiered in fall 1999, produced by Sunrise.

About the production: the story comes from an original script, there are 13 episodes of about 24 minutes and its current status is "finished".

Its main genres are action, mecha, mystery, psychological and sci-fi, with themes such as Super Robot, Amnesia, Philosophy and Noir.

On AniList, The Big O has an average score of 74%, a good score, and appears on 29,129 users' lists.

The franchise continues in or follows from: THE Big O (2003).

Paradigm City is a place without a past. 40 years ago, something happened that wiped the memories of everyone in it. Unfortunately, the people of Paradigm City were very busy before then, making Megadueses (giant robots) and monsters. People who were born after the memory wipe are gaining/recovering memories of the past and using them to build newer threats. With the help of The Big O (a faithful giant robot), his butler Norman and the android Dorothy, Roger Smith keeps Paradigm City safe. As problems mount and more memories surface, Roger's past and Paradigm's future begin to become suspect...

Official synopsis from AniList.